Control foe heating devices



Dec. 1, 1942. w. OLSEN CONTROL FOR A HEATING DEVICE Filed April 29, 1941Patented Dec. 1, 1942- 2,303,894 CONTROL FOB HEATING 'nnvrcas Ronald w.Olsen, Bloomfield,

N. J., assignor to General Electric Company, a corporation of New YorkAppueenonnpru 59 1941, Serial No. 390,964

14 Claims.

My invention relates to a control for a heatingdevice, and although notlimited thereto, it has particular application to a control for a stokerfurnace wherein aresponse to variations in the fuel bedair flowresistance is desirable.

An object of my invention is to provide' an improved automatic controlarrangement for controlling the feeding of air and solid fuel to aheating device differentially upon variation in the fuel bed air flowresistance.

Another object of my invention is to provide an improved arrangement forautomatically regulating the air flow through a fuel bed of variable Ithickness produced upon automatic operation of a fan means andautomatically initiating joint operation therewith of a fuel feedingdevice only when the air flow is above a predetermined minimum, and inaddition terminating operation of the fuel feeding device for a furnacein response to a predetermined fuel bed air flow resistance beingintroduced into the furnace.

A further object of my invention is to provide an improved stokerfurnace control for preventing operation of'a fuel feeding device inresponse to a movement of a constant combustion air flow control damperto a predetermined maximum open position.

A further object of my invention is to provide an improved furnacecontrol arrangement for controlling the rate of fuel feed in response tothe level of the outside temperature.

My invention will be more fully set forth in the following descriptionreferring to the accompanying drawing, and the features of novelty whichcharacterize my invention will be pointed out in the claims annexed toand forming a part of this specification. In the drawing, Fig. 1illustrates a control for a stoker-flred furnace which is provided-withembodiments of my invention, and Fig. 2 is a sectional side elevation ofthe air flow control arrangement employed in the furnace controlillustrated in Fig; 1. g

In the arrangement illustrated in the drawing, which shows an air flowcontrol for a stokerfired furnace for maintaining a flow of combustionair to the furnace within predetermined limits for varying conditions ofthe fire in the furnace, Iprovide a fuel feed switch responsive tomovement of the air flow control. Thus, the stoker, or fuel feedingdevice, is deenergized when the air flow control device moves to apredetermined or relatively wide-open position. I may also provide adamper control arrangement in the furnace flue, the movement of which isresponsive to outdoor temperatures for further controlling, through theair flow control and fuel feed switch arrangement, the rate of fueldelivery to the furnace.

Referring more particularly toFlg. 1 of the drawing, I have provided acontrol for a heating device, such as a furnace indicated generally bythe numeral I0, having a hopper H into which fuel, such as coal, may beplaced, a retort II on which the coal is burned, and a fuel feeding tubel3 connected between the hopper and the retort for conducting the fuelfrom the hopper to the retort. The fuel may be forced through the-fuelfeeding tube l3 in any suitable manner, such as through the movement ofa fuel feeding screw it. This screw may be rotated in any suitablemanner, such as by a feed motor l5. Any other suitable arrangement maybe provided for feeding fuel to the heating device. vIn order to providean arrangement for conducting combustion air into the retort, a duct i6is connected to the furnace and there is also provided any suitable airflow control arrangement for controlling the flow of air withinpredetermined limits, or for maintaining a substantially constant flowof air into the retort for varying The air flow control which I employwith my invention is described and claimed in my copending applicationSerial No. 390,961 and which is assigned to the same assignee as thispresent invention. This air flow control is shown in detail in Fig. 2and includes a damper ll pivotally mounted on a shaft extends throughthe fire bed conditions.

intake end of the'duct l6 and the duct is open on the sides and on thebottom. With such an arrangement lt is possible to maintain asubstantially constant flow of air through the ductl6 for varying backpressure conditions. Thus, the damper I! will rotate around its pivot l8against the biasing force produced by the weight member between theposition indicated in Fig. 2 and the dotted; line position H, forvarying conditions of system air flow resistance, in order to controlthe size of the passageway in the duct. Therefore, for a relativelythick fire bed the damper will assume a position as shown in Fig. 2,while for a relatively thin fire the damper will assume a position asindicated by the dotted lines 11, Any other suitable type of air flowcontrol may also be provided, such as the one described in my co-pendingapplication Serial No. 390,963, and which is assigned to the sameassignee as this present invention. In order to provide an outlet forthe.

products of combustion from the furnace, a flue l8. The end of thedamper.

rotating the fan 23.

' closing the contacts II and 33 .;,-the relay 21 may move to tion. Therelay the retort for varying conditions I3 is connected to the furnaceand a fan 23 is placed therein in order to induce the draft, or toprovide a pressure diflerence between the outside or intake end or theduct I3 and the end connected to the retort. Instead of employing aninduced draft, a forced 'drait, a natural draft. or any other draitproducing arrangement may be employed. A ten motor In order that the fanand feed motors may be energized from a suitable source of power, atransformer 22 is provided having its primary winding connected toincoming lines 23 and 24. Its secondary winding 25 has one side thereofconnected to an operating coil 23 of the relay indicated generally bythe numeral 21 through a conductor 28. In order that the coil 26 may beenergized when an increase in indicated generally by the nube placed inthe. room suitable place. This ondary winding 25 through conductors 33and 36, while the stationary contact 34 is connected to the oppositeside of the transformer winding 25 through conductors 31 and 28.thermostat 29 calls for heat it will be seen that the bimetallic strip33 will move to the left thus so that the coil 26 will be energizedthrough the circuit including one side of the transformer secondarywinding 25, conductor 23, coil 26, bimetallic strip 30, contacts 3i and33, and conductors 35 and 36. When the call for heat has been satisfiedthe thermostat w'ill move to its open circu1t position and then to theright so that the coil 23 will be short circuited through the contacts32 and 34 so that its inoperative posi- 21 is provided with a core 33and 33 and 34 are provided, the conv 2| is provided for g the heat ofthe provide a suitable temperature bimetallic strip 30 with contherein.when low resistance to the new of air I! need only be open a slightamount in order to allow a predetermined rate of air fiow into theretort. However, if the fuel bed is very thick it will provide a muchhigher resistance to the flow 0! air so that the damper l1 must move toa relatively wide open position in order to maintain the same rate ofair flowing to the retort. In-order to control the feed motor inresponse to fuel bed thickness any suitable circuit breaker arrangement,such as the switch 49, may be provided, the operation of which isresponsive to movement of the constant only a relatively and the damperair flow control arrangement which is employed.

The switch will remain closed when the fan motor is running and the firesistance, is below any predetermined maximum amount, but it opens whenthe air flow control which may be connected to the conductors 43 and 53,a pool of mercury 52 in the interior of the switch, and a centralportion which has a hole the hole is below the surface 0! the mercury itwill flow therethrough and make a" closed circuit between the hole 53will be above the when the damper has asmaximum the level a and remainso within any predetermined range contacts 39 and 40 which are operableto a circuit be energized. The energizing circuit for the fan motor maybe traced from the line 24 through conductor 43, contacts 43, conductors44 and 44,

through the fan motor, conductor 43, conductor The circuit for the feedline 24 through the conductor 43, contacts 43, conductor 44, ductor 48,a switch 43 which is operated by movement of the damper l1 and thefunction of which will be described in'more detail below, conductor 50,feed motor l5, conductors and 41, back to the line 23.

Instead of employing a thermostat in the space to be heated forinitiating the tion of the fan and fuel feed motors, any other such as athermostat responsive to furnace plenum temperature, or an aquastatresponsive to boiler water temperature, may be employed.

As described above and in my above first-mentioned copending applicationS. N. 390,961, the air flow control arrangement will move so as tomaintain a, substantially constant fiow of air into of the fire bed.Thus, if the fire bed is very light it will provide 41, back to the line23.

' through the of damper movement. Thus, the switch will close itscontacts when the damper has moved from the postion shown in Fig. 2 to aposition as indicated by the dotted lines 54 and will remain-closedduring movement of the damper between this position and the dotted lineposition ll, or minimum opening position. Itxwill be noted that amercury switch of the balanced disk or water type, which may be mountedon an axis passing through its center of gravity, is a desirable type toemploy when an air flow control of the type described above is employed.

since movement of the switch with the damper will not change the centerof gravity of the damper counter weight combination. Thus. air flowcontrol, the fuel feed motor on and off in order that no new coal willbe fed into the furnace if the bed has reached a predetermined maximumthickness,- this thickness being any suitable. value, such as that whichthe fan can just handle with the damper almost wide open. Thus,operation of the fuel feeding device is prevented when the may be turneddamper is operated to a predetermined maximum open position.

It will also is employed as shown that it assumes a position of mumopening when the fan is deenergized, that at the moment the thermostatcalls for heat the fan will be actuated first and the fuel feeding motorwill be actuated after the damper I] has moved into the range betweenthe positions indicated by the dotted lines 54' and H. with in Fig.2,which is biased so bed thickness, or reswitch contacts. The switch needonly be suitably placed on the substantially maxiconditions. .In orderto accomplish this a bellows 58 may be provided which has a bulb 51responsive to outdoor temperature conditions. A rod 58 and a suitablelinkage 59 are provided so that movement of the bellows may causecorresponding movement of the damper 55, When the damper 55has moved toa relatively closed position it will be in effect throttling or reducingthe eflectiveness of the fan 20, as it will be increasing the backpressure whichthe fanmotor must overcome. Conversely, if the damper 55is moved to a wide-open position it will present substantially noimpediment to the movement of the products of combustion through theflue. I

havefound that by moving the damper 55 from a wide-open position to aposition which throttles the fan motor, I am able to control the rate atwhich the fuel will be fed from the hopper to the retort. The rod andlinkage are, therefore,

the outdoor temperature is relatively cold, while the damper will bemoved to a relatively closed position during relatively warm weather.

open to a relatively wide open.position to try to maintain the air flowconstant and thus will cycle the fuel feed motor on and on, thusreduc'ing the total flow of fuel. In this manner I may control the rateof fuel feed to the furnace by varying the position of the damper 54,

since this in turn controls the, position of [the air flow controldamper 11. Such a control of the rate of fuel feed is particularlydesirable during mild seasons of the year, since in the spring and thefall a lesser amount of fuel feed is needed than in the cold weather.Thus. the bellows may be set so as to throttle the fan in the spring andthe fall and still provide relacold season of the year.

Although I have shown and describedparticular embodiments of myinvention, I do not desire to be limited to theparticular embodimentsdescribed, and I intend in the appended claims to cover allmodifications which do not depart from the spirit and scope of myinvention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A control for a furnace including .a fuel feeding device, a duct forintroducing combustion air into said furnace, fan means for producing aflow of air through said duct, air control means for maintaining asubstantially constant quantity of air flow through said duct forvarying conditicns within said furnace, means for initiating operationof said fan means when an increase in the amount of heat from saidfurnace is desired, means responsive to movement of said air controlmeans to predetermined positions for initiating and terminatingoperation of said fuel feeding means, and means responsive to changes inoutdoor temperature for varying the effectiveness of said fan means soas to control the rate of fuel feed to the furnace in response tooutdoor temperatures.

2, A control for a furnace including a fuel feed- When 1 the damper 55is nearly closed, damper i! will access in: device. a duct forintroducing combustion air into said furnace, fan means for producing anow of air through laid duct, air control means for producing asubstantially constant quantity of air flow through said ductfor varyingfire conditions within said furnace, this means connected to saidfurnace. means for initiating operation of said fan means when anincrease in the amount of minating operation of said fuel feeding means,

- and damper means within said flue, said damper means being movable inresponse to variations in outdoor temperature for controlling the rateof feed of said fuel feeding means. v 3. A control for a furnaceincluding a fuel feedconnected so that the damper is wide open whentively no impediment to its during the relatively ing device, a duct forintroducing combustion air into said furnace, fan means for producing aflow of air through said duct, air control means for producing asubstantially constant quantity of air flow through said duct forvarying fire conditions within said furnace, flue means connected tosaid furnace, means for initiating op-, eration of said fan means whenan increase in the amount of heat from said furnace is desired, meansresponsive to movement of said air control means to predeterminedpositions for initiating and terminatingoperation of said fuel feedingmeans, damper means within said flue, and thermostat means responsive tochanges in outdoor temperature for controlling the position of said fluedamper means.

4. In combination, a combustion heating device having a fuel bed, stokermeans for feeding fuel to increase the thickness of said fuel bed,independently operable fan means for producing a flow of combustion airthrough said fuel bed dependent upon the thickness thereof, an automaticflow responsive damper movably mounted in the path of said air flow formaintaining the flow within predetermined limits and having biasingmeans for maintaining said damper in'a predetermined position until saidair flow in- 45.

creases above the minimum limit, an automatic stoker control deviceresponsive to movement of said damper to said predetermined positionfor, preventing operation of said stoker means, and automatic controlmeans having connections for independently operating said fan means andhavlng other connections under the control of said stoker control deviceforoperating said stoker means jointly with said fan means only uponmovement of said damper from said predeter-;

mined position.

5. In combination, a combustion heating dcvice having a fuel bed, stokermeans for feeding fuel to increasevthe thickness of said fuel bed,separately operable fan means for producing a flow of combustion airthrough said fuel bed dependent upon the air flow resistance thereof, a

damper having automatic operating means reoperated by said automaticmeans for preventing operation of said stoker. means when .the flowresistance of said fuel bed exceeds said range, and

' automatic control means having connections for independently operatingsaid fan means and hav-- ing other connections under the control of saidmediate predetermined open and closed positions to maintain asubstantially constant air flow through said fuel bed upon variation inthe thickness thereof, and condition responsive means for controllingjoint operation of said fan means and said stoker means including meansfor preventing operation of said stoker means jointly with said fanmeans when said damper is operated to said predetermined open position.

"I; In combination, a combustion heating device asoasos the airflow-produced upon operation of said fan means for maintaining the rateof said air flow substantially constant upon variation in the flowresistance of said fuel bed within a predetermined range, separate airflow control means for controlling said air flow to predetermine saidrange, a stoker control device operated by said automatic means forpreventing operation of said stoker means when the flow resistance ofsaid fuel bed exceeds said range, and automatic control means havingconnections for operating said fan means and having other connectionsunder the control of said stoker control device for operating saidstoker means Jointly with said fan means when the flow resistance ofsaid fuel bed is within said predetermined range. 10. In combination, acombustion heating del vice having a fuel bed, stoker means for feedinghaving a fuel bed, stoker means for feeding fuel to increase thethickness of said fuel bed, separately operable fan means for producinga flow of combustion air through said fuel bed dependent upon thethickness thereof, means including a damper biased to a predeterminedopen position and having cooperating air flow directing means forvarying the position of said damper upon operation of said air flowproducing means to maintain the rate of air flow through said fuel bedsubstantially constant upon variation in j, the thickness of said fuelbed, stoker control switch means operated upon movement of said damperto said predetermined open position for preventing operation of saidfuel feed means, and automatic control means having connections foroperating said fan means and having other connections under the controlof said stoker control switch means for operating said stoker meansjointly with said fan means only upon movement of said damper from saidpredetermined open position.

8. In combination, a combustion heating device having a fuel bed, stokermeans for feeding fuel to increase the thickness of said fuel bed,separately operable fan means for producing a flow of combustion airthrough said fuel bed dependent upon the thickness thereof, meansincluding a centrally pivoted damper having balancing means for biasingsaid damper to the open position and having cooperating air flowdirecting means for varying the position of said damper upon operationof said air flow producing means to maintain the rate of air flowthrough said fuel bed substantially constant upon variation in thethickness of said fuel bed, balanced switch means operated upon movementof said damper to said open position for preventing operation of saidstoker means, and automatic control means having connections foroperating said fan means and having other connections, said balancedswitch means for operating said stoker means jointly with said fan meansupon movement of said damper from said predetermined open position.

fuel to increase the thickness of said fuel bed, separately operable fanmeans for-producing a flow of combustion air through said fuel beddependent upon the air flow resistance thereof,

means including a damper biased to a predetermined position and havingoperating means for varying the position of said damper upon operationof said air flow producing means to maintain the rate of air flowthrough said fuel bed substantially constant upon variation in the flowresistance of said fuel bed within a predetermined range, separatelyoperable damper means for restricting the flow of air through said fuelbed to predetermine said range, stokercontrol switch means operated uponmovement of saiddamper to said predetermined position for preventingoperation of said stoker means, and automatic control means havingconnections for operating said fan means and having other connectionsunder the control of said stoker control switch means for operating saidstoker means jointly with said fan means upon movement of said damperfrom said predetermined open position.

11. In combination, a furnace having a fuel bed, stoker means forfeeding fuel to increase the thickness of said fuel bed, separatelyoperable fan means for producing a flow of combustion air through saidfuel bed dependent upon the air flow resistance thereof, automatic meansfor energizing and deenergizing said fan means and having connectionsfor controlling the joint operation of said stoker means with said fanmeans, a damper having automatic operating means responsive to the flowof air through said fuel bed produced upon operation of said fan forpositioning said damper intermediate the open and closed positionsthereof for maintaining said flow of air through said fuel bedsubstantially j constant upon variation in the flow resistance of underthe control of said fuel bed within predetermined limits, and switchmeans for controlling said connections responsively to movement of saiddamper to the maximum open position for preventing operation of saidstoker means, said automatic operating means being biased to move saiddamper to said maximum open position when said fan is inactive.

12. In combination, a furnace having a fuel bed, stoker means forfeeding fuel to increase the thickness of said fuel bed, control meansfor 9. In combination, a combustion heating device combustion airthrough said fuel bed dependent upon the air flow resistance thereof, adamper having automatic operating means responsive to controlling theoperation ofsaid stoker means and operating means for said control meansineluding an automatic flow responsive damper for maintaining the flowof combustion air through said fuel bed substantially constant uponvariation of the fuel bed flow resistance within a prerange, and meansresponsive to variations in the outdoor temperature for-separatelyvarying the flow of air through said fuel bed to predetermine saidrange.

13. In combination, a furnace having a fuel bed, s'toker means forfeeding fuel to increase the thickness of said fuel bed, separatelyoperable fan means for producing a now of combustion air through saidfuel bed,.a damper having automatic operating means responsive to theair flow produced upon operation of said fan means for maintaining therate of said air flow substantially constant upon variation in the flowresistance of said fuel bed within a predetermined range,

means responsive to variations in the outdoor bed stoker means forfeeding fuel to increase 7 the thickness of said fuel bed, a fan forproducing temperature for separately varying the rate of air flowthrough said fuel bed to predetermine said range, and means responsiveto movement of said damper to the maximum open position for preventingoperation of said stoker means 'when theflow resistance of said fuel bedexceeds said range.

14. In combination, a furnace having a fuel a flow of combustion airthrough said fuel bed, condition responsive means for starting andstopping operation of said fan, means. including a centrally pivoteddamper having balancing means for biasing said damper to the openposition and having cooperating air flow directing means for

